西秦岭大草滩群的沉积环境及构造意义  

Sedimentary environment and tectonic significance of the Dacaotan Group of the Western Qinling Mountains

作　　者：闫臻[1,2] 王宗起[3] 王涛[3] 闫全人[3] 

机构地区：[1]中国科学院地质与地球物理研究所岩石圈开放实验室 [2]中国地质科学院地质研究所北京100037 [3]中国地质科学院地质研究所

出　　处：《地质通报》2002年第8期505-515,共11页Geological Bulletin of China

基　　金：中国地质调查局地质调查项目(DKD2001002);国家自然科学基金项目(49972074;40172071)资助。

摘　　要：沉积序列、沉积相、古水流和物质组成的研究结果表明,西秦岭大草滩群和铁山群分别是由冲积扇和近岸浊积扇形成的陆相碎屑岩组合和滨海相浊积岩。李子园群岛弧火山岩不仅是形成大草滩群的沉积物源,而且也是大草滩群沉积盆地的基底。构造变形特征和与上、下地层接触关系综合研究显示,大草滩群是秦岭晚古生代弧前增生过程中形成的一个逆冲席顶盆地。大草滩群可与祁连山中晚泥盆世沙流水群和雪山群相比较,向东、南分别与同期异相桐峪寺组、铁山群相对应,显示出由北向南、由西向东的构造迁移特征。The Upper Devonian Dacaotan and Tieshan groups are composed of nonmarine clastic rocks and littoral turbidite in the western Qinling Mountains.Their sedimentary facies,sequences,detrital composition and paleocurrents indicate that the Dacaotan and Tieshan groups in an alluvial fan and littoral turbidity fan,respevtively.Volcanic rocks of the Liziyuan Group originated from an island arc.They are main sedimenta-ry source of the Dacaotan Group,and also the basement of the Late Dvonian sedimentary basin.On that basin,and on account of the characteristics of the structural deformation and the contact of the Dacaotan Group with its basement,the authors propose that the Dacaotan Group is the depositional fills of a thrust sheet-top basin formed during the Late Palaeozoic forearc accretion,rather than the direct products of Ear-ly Palaeozoic orogeny in the Qinling.According to regional data,the Dacaotan Group can be compared with the Middle-Upper Devonian Shaliushui and Xueshan groups of the Qinling mountains,and to the east and south it may correspond to the contemporaneous Upper Devonian Tongyusi Formation and Tieshan Group of different facies.This shows a tectonic migration from north to south and from west to east.

关 键 词：秦岭 大草滩群 铁山群 晚古生代 逆冲席顶盆地 构造迁移特征 沉积环境 

分 类 号：P544.4[天文地球—构造地质学] P542[天文地球—地质学]